The present invention broadly relates to the art of resistance roll-welding machines--also referred to as electrical resistance-roll seam welding machines--and, more specifically, is concerned with a new and improved construction of a welding roll arrangement for such resistance roll-welding machine, which is of the type comprising a welding arm arranged at the machine frame and an electrode roll mounted at an end of the welding arm, the welding current being delivered to the electrode roll by means of the welding arm which functions as an electrical conductor and the shaft of the electrode roll which is mounted in such welding arm.
With heretofore known resistance roll-welding machines of the previously described type, the front end of the welding arm, which is of fork-like or bifurcated structure for the reception of the electrode roll, is divided in a plane extending along the shaft center of the electrode roll, and in each of the parts there is formed a semi-circular-shaped bearing trough or cradle for the reception of the shaft. The shaft is fixedly clamped between the parts which are interconnected with one another by screws. To produce a clamping action with this construction, it is necessary to provide a spacing between the parts in the separation or parting plane and which parts are interconnected by the screws extending perpendicular to the parting plane.
This type of mounting of the electrode roll has been chosen in order to be able to exactly adjust its elevational position, so that it is dispositioned in the proper location with respect to other machine parts serving for guiding the workpieces which are to be welded to the electrode rolls. For this purpose the shaft is eccentric with regard to the roll which is rotatably mounted thereon. Hence, to carry out the desired adjustment the clamping screws must be loosened in order to be able to rotate the shaft.
A notable drawback of this manner of attaching the electrode roll-shaft in the welding arm resides in the fact that owing to the bearing fork which is divided at the center of the shaft, the current flow from the welding arm to the shaft at the one side is accomplished without any difficulty by means of the semi-circular-shaped bearing cradle, yet the current flow to the end of the bearing fork which is pressed against the shaft at the other side of the parting plane can only be accomplished by means of the screws serving for fixedly clamping the shaft. This circumstance obviously is associated with a poorer current transfer or flow than would be the case if there were not present any reduction in the cross-section at the current conducting path, since then there would be present a smaller contact or transfer resistance and a smaller voltage drop, resulting in lower heat development at the electrode roll. By virtue of the fact that all possible expedients are employed for cooling the electrode roll, it is therefore of decisive importance if the development of heat, associated with the current transfer, is maintained as small as possible.
In the case of the heretofore known resistance roll-welding machines having the described electrode roll mounting or support at the end of the welding arm, it is furthermore to be noted that the bearing fork end serving for fixedly clamping the shaft of the electrode roll is constructed as a general rule as a support or directly connected with a support in which there are mounted working tools following the electrode rolls, such as for instance a pressure roll. Frequently there are also connected further auxilliary devices at the end of the welding arm which is mounted in a cantilever fashion at the machine frame. The welding arm is located internally of the body of the workpiece which, after the welding operation, has a cylindrical shell-like configuration, and it is for this reason for instance that there can be arranged a device for applying lacquer or varnish or the like to the inside of the finished welding seam also at such type support at the end of the welding arm.
A further drawback of the state-of-the-art electrode roll mounting arrangement resides in the fact that for the adjustment of the electrode roll, by adjusting the eccentric shaft relative to the roll, it is necessary to release the clamping screws at the bearing fork end each time, and therefore, to equally loosen the support carrying the subsequently arranged working tools, and after accomplishing the adjustment of the electrode roll to again fixedly clamp such in exact alignment with the welding arm. A further difficulty which is associated with this construction resides in the fact that owing to the spacing at the parting or separation plane of the bearing fork and which is needed for obtaining a clamping action, the exact adjustment of the support in aligned relationship with regard to the welding arm requires each time a great deal of attention.